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Governors

Governors. Governors. Governors serve three basic purposes: Maintain a speed selected by the operator which is within the range of the governor. Prevent over-speed which may cause engine damage. Limit both high and low speeds. Governors.

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Governors

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  1. Governors

  2. Governors • Governors serve three basic purposes: • Maintain a speed selected by the operator which is within the range of the governor. • Prevent over-speed which may cause engine damage. • Limit both high and low speeds.

  3. Governors • Generally governors are used to maintain a fixed speed not readily adjustable by the operator or to maintain a speed selected by means of a throttle control lever. • In either case, the governor protects against overspeeding.

  4. How does it work? • If the load is removed on an operating engine, the governor immediately closes the throttle. • If the engine load is increased, the throttle will be opened to prevent engine speed form being reduced.

  5. Example • The governor on your lawnmower maintains the selected engine speed even when you mow through a clump of high grass or when you mow over no grass at all.

  6. Pneumatic Governors • Sometimes called air-vane governors, they are operated by the stream of air flow created by the cooling fins of the flywheel.

  7. Air-Vane Governor • When the engine experiences sudden increases in load, the flywheel slows causing the governor to open the throttle to maintain the desired speed. • The same is true when the engine experiences a decrease in load. The governor compensates and closes the throttle to prevent overspeeding.

  8. Centrifugal Governor • Sometimes referred to as a mechanical governor, it uses pivoted flyweights that are attached to a revolving shaft or gear driven by the engine.

  9. Mechanical Governor • With this system, governor rpm is always directly proportional to engine rpm.

  10. Mechanical Governor • If the engine is subjected to a sudden load that reduces rpm, the reduction in speed lessens centrifugal force on the flyweights. • The weights move inward and lower the spool and governor lever, thus opening the throttle to maintain engine speed.

  11. Vacuum Governors • Located between the carburetor and the intake manifold. • It senses changes in intake manifold pressure (vacuum).

  12. Vacuum Governors • As engine speed increases or decreases the governor closes or opens the throttle respectively to control engine speed.

  13. Hunting • Hunting is a condition whereby the engine speed fluctuate or is erratic usually when first started. • The engine speeds up and slows down over and over as the governor tries to regulate the engine speed. • This is usually caused by an improperly adjusted carburetor.

  14. Stability • Stability is the ability to maintain a desired engine speed without fluctuating. • Instability results in hunting or oscillating due to over correction. • Excessive stability results in a dead-beat governor or one that does not correct sufficiently for load changes.

  15. Sensitivity • Sensitivity is the percent of speed change required to produce a corrective movement of the fuel control mechanism. • High governor sensitivity will help keep the engine operating at a constant speed.

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